The electricity system operator at National Grid has published draft de-rating factors for renewables participating in the capacity market.

The preliminary figures give an early indication as to how much they would be considered to contribute to security of supply and therefore how generously they would be compensated.

As the EMR delivery body, National Grid Electricity System Operator has been tasked with developing a de-rating methodology for renewables should they be allowed to enter the capacity market in future.

It is undertaking the work after the government announced in August that unsubsidised renewables could be permitted to take part upcoming auctions.

Capacity market de-rating factors are intended to reflect the expected availability of different technologies during system stress events and are typically set in line with historical performance. Participants bid, and are paid, according to their de-rated capacity.

Based on the methodology it is developing, National Grid has suggested offshore wind projects could be expected to receive a de-rating factor of less than 15 per cent for delivery in 2020/21, and onshore wind projects less than 9 per cent. The figure for solar is by far the lowest at little more than 1 per cent.

For comparison, the de-rating factor for combined-cycle gas turbines has been set at 89 per cent for 2019/20.

Indicative de-rating factors

Source: National Grid Electricity System Operator

The capacity market is currently suspended after an EU court overturned a 2014 decision by the European Commission to approve the mechanism under state aid rules. The government is planning to hold a T-1 auction over the summer and a T-3 auction in 2020 to replace those previously scheduled for early 2019.

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